In recent years, a hybrid-type construction machine of which a part of a drive mechanism is electrically driven is suggested. Here, in this specification, a “hybrid-type construction machine” refers to a hybrid construction machine. Such a construction machine is equipped with a hydraulic pump to hydraulically drive a work element, such as a boom, an arm and a bucket, in many cases. Generally, a hydraulic pump is driven by an engine. Then, a motor generator is connected to the engine, which drives the hydraulic pump, via reduction gears. The motor generator assists a drive of the engine, and the electric power obtained by generation-operating the motor generator is charged to a capacitor.
There is suggested a construction machine, which is equipped with an electric motor in addition to a hydraulic motor as a power source of a turning mechanism to turn an upper part turning body, wherein a drive of the hydraulic motor is assisted by the electric motor when accelerating the turning mechanism, and a regenerating operation is performed by the electric motor when decelerating the turning mechanism to charge the generated electric power to a battery (for example, refer to Patent Document 1).